Sprayed metal coating



Allg- 26, 1952 B. v. MGBRIDE V' 2,607,983

SPRAYED METAL COATINGY Filed June 8. 1946 WITNEssEs:

Patented Aug. 26, 1,952

SPRAYED METAL COATING Byron V. McBride, Irwin, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June s, 194s, serial No. 675,431k

'Ihis invention relates to protective coatings comprising sprayed metal for application to base members.

The object of this invention is to provide for applyingv to members highly protective sprayed metal coatings.

A further object of this invention is to provide for applying to members highly protective coatings composed of sprayed metals and a corrosion inhibitor embodied therein.

Astill further object of the invention is to provide a composition composed of a sprayable and'fusible metal and a corrosion inhibitor associated therewith.

Other objects of the invention will in part be obvious and will in part appear hereinafter. For

abetter understanding of the nature and ob-..

jects of the invention, reference should be had to the following detailed description and drawing, in which:

Figure 1 is a view in elevation, partly in section, of one method of providing the protective coating of the invention;

Fig. 2 is a view in elevation, partly in section, of a sprayable rod member for carrying out the process of the invention;

Vliig. 3 is a vertical cross section through a modicationv of a sprayable rod member;

Fig. 4 `is alcrossrsection through a particle capable' of being sprayed; and

Fig', 51is a fragmentary view in elevation, partly in cross section, of anotherform` of apparatus forcarrying out. the invention. y

In providing protective coatings on various base members, it has been found that sprayed metal alone is often subject to corrosion or premature failure because of the porosity of the sprayed metal coating when applied in reasonable thicknesses. protective coatings of sprayed metal having exceptionally high protective value are produced byembodying. in thesprayed metal a corrosionV inhibitor. Suitable corrosion inhibitors are the corrosion resisting compounds of chromium such,

Only 'a minor proportion of the protective According to the present invention,

4 Claims. `(Cl. 253-1962) y coating need be composed of the corrosion lnhibitor. As little as 0,1% of the inhibitor will give beneficial results, While 5% to 20% or more will produce excellent protective coatings. Discoloration of the metal base or the sprayed metal will be greatly retarded. Corrosion of the base metal will be reduced.

The 4corrosion inhibitor may be applied in av number of Ways for incorporating into the coating of sprayed metal. A convenient method is to substantially simultaneously spray a solution of the corrosion inhibitor in a volatile solvent at the area Where the metal is being sprayed IVon The heat from the sprayedfv metal will rapidly evaporate the' volatile solvent.'

a base member.

present in the solution of the corrosion inhibitor'f thereby leaving the corrosion inhibitor embodied v in the sprayed metal coating.

Referring to Fig. 1 of the drawing, there isillustrated a base member I0 of a ferrous metal,

such as steel for example, upon the surfacesof which a protective coating is to be applied. A `metal spray gun I2, such as a Schoop spray gun,

which may be heated electrically or by means of gas or other combustible material, and provided with a source of compressed gas to'eject a spray of molten metal, is supplied with a v'vire or rod I4 of a suitable metal for producing a pro,-A

tective sprayed coating. The Wire or rodl I4, for example, may be composed of zinc, cadmium, aluminum, lead, copper, tin, nickel, Monel metal,

stainless steels, such as- 18% nickel ancl` 8% chromium alloys, silver or other noble'metal.A In operation, the metal spray gun I2 creates a ame of an intense heat in which the Wire or rod I4 is fused and is immediately subjected j'to a surface condition may beproduced on thebas'e member I0.V The sprayed metal coatings'fmay' be less than 0.001 inch thick up to 0.025 inch heavy, and in extreme cases le inch thick orheavier.

A conventional liquid spraying device I8, such,

for instance, as a paint sprayer, lprovided with a container 20 carrying a solution of a corro-V sion inhibitor is operated to direct a spray 2 2 of the solution of corrosion inhibitor at the area 24V where the metal spray I6 is impinging, or just previous to,-or just subsequent to the passage of the spray I6, vThe solution of Vcorrosion ln-'rA hibitor is preferably but not necessarily, an4

application with the sprayed metal is as follows:

Sodium dichromate grams-- 240 Sulphuric acid s do 2.4 Water to,make j V litre 1 It will be found that heat from the sprayed metal will evaporate the water from the solution with this solution leaving sodium dichromate intimately associated with thesprayed metal particles. 1

Exemplary ofthe improvement produced by the practice of the invention two similar panels were prepared: One panel was sprayed with .zinc

alone using the spray gun I2 of Fig. 1j and the second panel also was coated with zinc except that a sodium dichromate, solution in the above example was applied simultaneously with the sprayedl zinc, vWhen subjected to salt spray tests, the rst panel with the coating of sprayed zinc alone thereon'was crustedwith white corrosion products in about 100 hours, while the second panel produced according to this invention was free from such corrosion products. After 576 hours in the saltspray cabinetfthe first zinc` coated panel was heavily crusted with white salts, whereas only a small fraction of the second panel had any white corrosion product present thereon. Y

.1t is not necessary toemploy corrosion inhibitor. The corrosion inhibitor maiT besembodied in the wire or rod of fusible metal whichjforms the base of the -sprayed metal coating.l The wire or rod may be associated in agreat number of ways with the corrosion 1n.

hibitor,.and both simultaneously fused and sprayed.` It will be apparent that best results will Ybe obtained if the corrosion inhibitor kis fused, 'rbutvit need not fuse and may projected along with thelmolten spray metal as a finely divided powder.

Referring to Fig. 2 of the drawing,lthere is illustrated a wire or` rod -30 suitable for use in spray gun l2 composed of a hollow tube 32 carry-l s ing the corrosion inhibitor 34 within the hollow. The tube 32 Ymay be prepared from zinc, aluminumffl'ead, tin, copper, and silver or other noble metal.k The corrosion inhibitor may be alkali metal'chromate or dichromate, or Vother metal chromate, such, for example, as lead chromate, zinc chromate, or the corrosion inhibitor'may be a zinc phosphate or the like.

The wire or vrod may `be coated with a `thin surface layer of the corrosion inhibitor applied thereto as a paste or from a solution. Stranded wire may be coated by extruding thereon a pasty mixture of the corrosion inhibitor. If desired. the exteriorcoatings of corrosion inhibitor on a'protective sheath composed of metal or aprotective resin 'or the like: f

use in a metal spray gun composed of a body-"38 of, the fusible metal such as zinc, lead, cadmium or the like provided with several grooves 40 carry-,.-

ing therein a supply of corrosion inhibitor 42. The element 36 may be Vfed into the spray gun I2'y in the normal manner, and vwhen sprayed from `a metal spray gun will provide a spray composedA of metal particles and .fused particles of corrosion inhibitor. -Upon impinging a basemember and cooling, alprote'ctive coating having-L a solution of thev 4 unusually good protective characteristics will be secured.

The protective coatings of this invention can be applied by the spraying of fine powders of various metals, the powders carrying coatings of corrosion inhibitors, or otherwise associated with the inhibitors. Thus the metal powder may be admixed rwith .powdered'inlzr'ibitorr` 'Several different powdered metals and one or more inhibitors may be coated thereon or admixed therewith.

In Fig. 4 of the drawing there is illustrated a greatly enlarged particle of a metal 46 such as aluminum, cadmium, zinc, or the like with a surface .coating 48 of a corrosion inhibitor. The coating '48 may be produced by immersing the fine metal powder in a solution of the corrosion inhibitor and drying the wetted powders or else by. dipping'the metal powder in chromic acid or the fusible metal wire 'or rod may beY covered with i phosphoric acid wherebyf a reaction is produced leaving -a phosphate or chromatecoating on each particle. The treated powder may be appliedby a suitable device such as a Schoop spray gun.

As shown in Fig. 5 of the drawing, the metal powders may be applied by means of `the flame sprayer 50 having a central passage 52- for feeding the coated metal powder therethrough. The passageways k54 and 56 provide for a supply of combustible gas and compressed air in .order to produce a flame 58 ofsuiiicient temperature-to fuse the metal powder andto -project the molten particles vas a spray. The .fused metalpowderfenveloped in combusted .gasis projected as a spray 60 againstl the metal surface base .member fill whereby a coating .62 composed of a-n .intimate mixture of metal and .corrosion-inhibitor is deposited. The coating 62 of sprayed metal will be found to ,be tenaciously adherent to the metal s surfaces of the base member.

Aluminum metalY in powder form ner than mesh was mixed with zinc chroma'te .in an amount equal to 5% of the weight of the aluminum. Steel panels sprayed with the powder mixture produced a coatingl of an appearance equally attractive and otherwise similar to Ythat.

secured with an all aluminum powder. lHowever.. on subjecting the steel panels to salt spray tests, it was `found that after hours the plain aluminumA coating had not prevented the corrosion of the ferrous metal l and the .aluminum coating was covered withafheavy discoloration' The ycoating produced from Fig. 5 to provide a coatingof about 0,005 inchv thick. Another set of steel panels were similarly sprayed with plain zinc alone. Accelerated `cor-- rosion tests were made of both 'sets of panels."

After 200 hours in a salt spray test the plain zinc was thickly coated with a whitelm yor corrosion productswhile the coating composed lof .zi-nc and sodium dichromate was `'clean 'and :exhibited lnoi apparent corrosion When-tested iin a himidity cabinet at 100% relatively humidity at I25" C.; planr .zinc coated panels were coated with. a loose. white powdery nlm.' Panelsxcoated lwith zinc plus' 10% sodium '.dichromate were of a clean gray appearance and had no apparent' corrosion.. Whlethe sprayedlnetai 'coatings containing a corrosion inhibitor are applicable to almost any type of material, such, for example, as metals, ceramics, glass, wood, and the like, the protective coatings are most advantageous when applied Ato ferrous metals or other easily corrodable metals. Electrical apparatus exposed to the outdoors atrnosphere such as transformers, capacitors, switchgear, and the like may be protected to advantage by means of this invention. However, indoor and outdoor atmospheres will be resisted by hardware, machinery, household appliances and the like coated with the compositions herein disclosed. The corosion inhibitor may function not only to protect the base metal such as iron or steel to which the sprayed metal coating is applied, but may furnish corrosion resistance to the sprayed metal itself. Thinner coatings may be applied to apparatus with as good protection as heavier coatings of sprayed metal without inhibitor.

While the corrosion inhibitor and sprayed metal coatings of this invention possess properties indicating their use as protective coatings proper, it will be appreciated that the compositions have advantages desirable for other purposes where weather resistance may be secondary. Thus in building up parts the enhanced corrosion resistance of the compositions imparts benefits not had by plain sprayed metal deposits.

Since certain changes may be made in the above invention and different embodiments Vof the invention could be made Without departing from the scope thereof, it is intended that al1 matter contained in the above description or taken in connection with the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. An article of manufacture comprising. in combination, a ferrous metal base member and a protective coating applied to the surface of the base member, the coating comprising essentially sprayed porous metal and a corrosion inhibiting compound selected from the group consisting of phosphate and chromium compounds embodied both on the exposed surfaces and in the body of ythe sprayed metal.

2. An article of manufacture comprising, in combination, a metal base member and a protective coating applied to the surface of the base member, the coating comprising essentially sprayed porous zinc metal and a corrosion inhibiting chromium compound embodied both on the exposed surfaces and in the body of the sprayed metal.

3. An article of manufacture comprising, in

combination, a metal base member and a protective coating applied to the base member, the coating comprising sprayed porous aluminum metal and a corrosion inhibiting chromium compound embodied both on the exposed surfaces and in the body of the sprayed metal. v4. An article of manufacture comprising, in combination, a metal base member and a protective coating applied to the base member, the coating comprising sprayed porous cadmium metal and a corrosion inhibiting chromium compound embodied both on the exposed surfaces and in the body of the sprayed metal.

BYRON V. MCBRIDE..

REFERENCES CITED `The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,299,988 Metzger Apr. 8, 1919 1,669,643 Andrews May 5. 1928 1,971,804 Alexander Aug. 28, 1934 1,978,115 Collins Oct. 30, 1934 1,980,890 Tompkins Nov. 13, 1934 2,110,717 Sellers Mar. 8, 1938 2,121,574 Romig June 21. 1938 2,206,502 Heligiman July 2, 1940 2,234,206 Thompson Mar. 11, 1941 2,333,206 Sloan Nov. 2, 1943 2,391,656 Tanner Dec. 25, 1945 12,412,543 Tanner Dec. 10, 1946 2,414,923 Batcheller Jan. 28, 1947 OTHER REFERENCES v The Corrosion of Metals, pp. 204, 211-213, 1926. Pub. by Edward Arnold 8: Co., London, England. (Copy in Div. 3.) A

Metal Finish pp. 148, 149,v Apr. 1945. (Copy in Div. 14.) v 

1. AN ARTICLE OF MANUFACTURE COMPRISING, IN COMBINATION, A FERROUS METAL BASE MEMBER AND A PROTECTIVE COATING APPLIED TO THE SURFACE OF THE BASE MEMBER, THE COATING COMPRISING ESSENTIALLY SPRAYED POROUS METAL AND A CORROSION INHIBITING COMPOUND SELECTED FROM THE GROUP CONSISTING OF 